Sub-Boreal Spruce Biogeoclimatic Zone Research Articles

Spatial scale of stand-replacing forest disturbance influences the amplitude of snowshoe hare population fluctuations in boreal forests of northwest Canada

Spatial scale of stand-replacing forest disturbance influences the amplitude of snowshoe hare population fluctuations in boreal forests of northwest Canada

A Site Index Model for Lodgepole Pine in British Columbia

A height growth and site index model was developed combining permanent sample plot (PSP) and stem analysis (SA) data from the Sub-Boreal Spruce biogeoclimatic zone of British Columbia, Canada. SA data were screened for indications of early suppression, virtually eliminating that source of bias. Estimation was based on a stochastic di erential equation form of the Bertalan y-Richards growth curve, including environmental and measurement/sampling variation. Methods involve the inclusion of mixed e ects, and obtaining simultaneous maximum likelihood estimates for all the parameters. Di erences in error structure between PSP and SA data were taken into account. The model fits the data well, and compares favorably to existing alternatives.

A Parsimonious Dynamic Stand Model for Interior Spruce in British Columbia

Abstract A whole-stand growth model, Scube, was developed for spruce-dominated, even-aged, natural and planted stands, using permanent sample plot data from the sub-boreal spruce biogeoclimatic zone of British Columbia, Canada. Available data were limited, with no information on mature planted stands or thinning treatments. A parsimonious model design, incorporating knowledge of stand dynamics and experience from other forests, made possible a logical reproduction of observed behavior and plausible extrapolations to other conditions. Scube consists of a system of four differential equations, describing the evolution of four state variables: top height, trees per hectare, basal area, and a stand closure indicator. Concepts of closure and site occupancy drive the behavior of young stands and the response to thinning. Parameters were estimated through numerical optimization of several residual functions, reflecting different projection interval types and weighting strategies. Differences in estimates among the various criteria were small. Calculations are facilitated through expressions that remain invariant in the absence of disturbances. The methods generalize the algebraic difference approach and related forest modeling techniques, linking them to standard dynamical systems theory.

Stable isotope tracing of fertilizer sulphur uptake by lodgepole pine: foliar responses

A plot-scale fertilizer sulphur (S) stable isotope tracer study was established in 2001 in the Sub-Boreal Spruce biogeoclimatic zone in central interior British Columbia where S deficiencies are common in lodgepole pine ( Pinus contorta var. latifolia Engelm. ex S. Wats.) stands. Treatments used operationally realistic applications of 300 kg N·ha–1 as urea and 100 kg S·ha–1 as either sulphate (SO4) or elemental S (S0). δ34S values of fertilizer S differed by >9‰ from pretreatment δ34S values of total S in foliage at the two study sites (5.2‰ and 8.2‰). These differences enabled quantification of fertilizer uptake using isotopic analysis of post-treatment foliar S. Addition of K2SO4 with δ34S of +17.5‰ increased foliar δ34S by 3.5‰ and 6.6‰ at the two sites, respectively, in the year after treatment, indicating fertilizer contributions >40% to foliar total S. For a S0 fertilizer application with a δ34S value of +19.3‰, foliar δ34S increases were smaller but steadily increased, resulting in an average tracer S uptake of ~20% over three years. These results confirmed the more rapid availability of S from SO4-based fertilizers and demonstrated the feasibility of field tracer experiments using stable S isotopes at natural abundance levels.

Verification of a Forest Rating System to Predict Fisher, <em>Martes pennanti</em>, Winter Distribution in Sub-boreal Forests of British Columbia, Canada

This study verified the ability of a forest rating system to predict the winter distribution of Fisher (Martes pennanti) in the Sub-boreal Spruce Biogeoclimatic Zone of central interior British Columbia. Forest polygons (i.e., homogenous areas with similar forest stand characteristics) were classified according to their age and structural development, canopy closure, basal area in mature trees, average tree diameter at breast height, and percentage of shrub cover. Approximately 170 km of transects randomly distributed across polygons were inventoried (snowshoed) from December to February 2005-2008. A total of 278 Fisher tracks were recorded. The observed frequency of Fisher tracks per polygon type was significantly (P < 0.05) different from expected. The majority (245 or 88.1%) of tracks were recorded in excellent- and high-quality polygons corresponding mostly to mixed coniferous stands. On average, these stands were 138.2 years old, and had 54.4% canopy closure, 38.1 m2/ha basal area, 27.8 cm dbh, and 11.4% shrub cover. This study showed that the forest rating system was adequate to predict Fisher winter distribution, and could be used to develop forest management plans that are compatible with the species habitat requirements.

A height-growth and site-index model for interior spruce in the Sub-Boreal Spruce biogeoclimatic zone of British Columbia

Height growth was modelled for spruce-dominated, even-aged stands in the Sub-Boreal Spruce biogeoclimatic zone of British Columbia, Canada, using both stem analysis (SA) and permanent sample plot (PSP) data. The model is based on a stochastic differential equation (SDE) formulation of the Bertalanffy–Richards growth equation. The SDE approach accounts for serial correlation and heterogeneous variance and makes hypothesis testing possible. Statistically significant differences in height–age trends between SA and PSP data were found that may be attributed to bias caused by dominance changes in SA trees. Error structure in SA and PSPs was also significantly different. Combining both data sources in a way that respects these different error structures reduced bias and increased precision. Four parametrizations were tested; the best was a polymorphic version. The final model fit the data well with no appreciable bias over the full range of ages and site qualities. The currently used spruce site-index model was found to underestimate growth and overestimate site index in young stands. The new model can be recommended for height prediction and site-quality assessment in interior spruce.

Riparian alder ecosystems as epiphytic lichen refugia in sub-boreal spruce forests of British Columbia

Alder-dominated riparian forests represent only a small proportion of the landscape in central-interior British Columbia. However, they possess a suite of attributes that may allow them to function as refugia for canopy macrolichens. These include their deciduous habitat, their location in moist nutrient receiving sites, and their distribution as narrow corridors that cross broad regional landscapes. We have examined their potential role as lichen refugia by assessing canopy macrolichen communities in 75 riparian alder forests across a 200 km longitudinal gradient in central-interior British Columbia. Study sites were stratified equally between three climate subzones of the Sub-Boreal Spruce biogeoclimatic zone. Forty-nine macrolichen taxa were observed, including the old-growth indicator cyanolichen species Lobaria scrobiculata (Scop.) DC., L. retigera (Bory) Trevisan, Nephroma isidiosum (Nyl.) Gyelnik, and Sticta limbata (Sm.) Ach. Canonical correspondence analysis identified mean annual temperature, mean annual precipitation, age of adjacent conifer forest, and abundance of large stems (dbh >10 cm) as significant explanatory variables. Regional precipitation gradients explained the exclusion of many lichen species from both the most westerly and most easterly riparian forests, with drier summer conditions and heavy winter snowpack, respectively, being major limiting factors. Lichens preferentially occupied large leaning stems, which may provide greater precipitation interception and continuity of substrate, when compared with smaller upright alder stems. We conclude that alder-dominated riparian forests represent a major refugium for old-growth dependent lichens in British Columbia’s sub-boreal spruce landscapes and as such may provide valuable dispersal corridors between remnant old-growth coniferous forest patches.

Decomposition of pure and mixed foliage litter in a young lodgepole pine – Sitka alder stand in the central interior of British Columbia

A 7-year litterbag experiment examined mass loss dynamics of Sitka alder ( Alnus viridis (Chaix) DC. subsp. sinuata (Regel) A. Löve & D. Löve) and lodgepole pine ( Pinus contorta Dougl. ex Loud. var. latifolia Engelm. ex S. Watson) foliage litter in a young stand dominated by these species in the Sub-Boreal Spruce biogeoclimatic zone of central British Columbia. Although mass loss was initially faster for alder litter, the amounts of mass remaining for alder, pine, and mixed pine–alder (50:50 by mass) litter began to converge after 2 years. Mass loss by the mixed litter differed significantly from that predicted from the behaviour of its pure components, but the mechanisms responsible could not be determined from this experiment. Limit values for the projected maximum extent of mass loss ranged from 63.5% (alder) to 76.9% (pine), with the latter value considerably below estimates reported for lodgepole pine in Scandinavia. Despite these differing limit values, forest floor mass measurements prior to the experiment did not show significantly higher organic matter accumulations under long-established alder clumps on this site.

Site-Dependent Height-Age Models for Paper Birch in British Columbia

In British Columbia, foresters use the height-age models for trembling aspen (Populus tremuloides Michx.) from the neighbouring province of Alberta to predict height and site index for paper birch (Betula papyrifera Marsh.) because height-age models for paper birch in British Columbia do not exist. The aspen model has not been extensively tested for local use on paper birch trees. Consequently, it is not known how well they predict the height growth of site trees. We rectified this situation by developing paper birch height-age models from locally collected stem analysis data for paper birch. Data from 61 plots in the Interior Douglas-Fir, Interior Cedar and Hemlock, and Sub-Boreal Spruce biogeoclimatic zones were fit to a model based on the log-logistic function. Differences in growth patterns between the zones were detected using indicator variables. This height-age model should be used for paper birch in the sampled biogeoclimatic zones in British Columbia because it is the best fitting model. An alternative model is available for sites not in the sampled zones. A comparison of the trembling aspen model and the paper birch model indicates that the difference between the models is small over most of the management age range of paper birch. The exception to this is at young ages and high site indexes, where paper birch is predicted to be taller than trembling aspen.

Effects of compaction and water content on lodgepole pine seedling growth

Soil disturbance by heavy machinery usually causes a decrease in porosity and an increase in soil strength, which may limit access to nutrients and compromise seedling survival and growth. This study used a soil strength and a greenhouse experiment to assess the impact of compaction on lodgepole pine ( Pinus contorta Dougl. Ex. Loud. var. latifolia Engelm.) seedling growth and the degree to which soil water influences the effects of compaction. A silt loam soil was collected from a forest landing in the central interior of British Columbia (BC) in the Sub-Boreal Spruce Biogeoclimatic zone. The silt loam soil was used in a soil strength experiment where soil with four water content levels (0.10, 0.18, 0.27, and 0.36 cm 3 cm −3 ) was packed into 0.21 cm 3 cores with three levels of compaction (74, 79, and 84% of maximum bulk density (MBD)). Soil strength was strongly affected by compaction and water content. In the greenhouse experiment, three water content levels (0.10–0.15, 0.20–0.30, and 0.30–0.35 cm 3 cm −3 ) and three levels of compaction (67, 72, and 76% of MBD) were applied to soil in pots and 1-year old lodgepole pine seedlings were grown in the pots. Soil strength was highest (1275 kPa) for the high compaction and dry water content treatment in the greenhouse experiment. Though the soil strength for this treatment did not exceed 2500 kPa, the effect of compaction on growth was noticeable, with a decrease in diameter growth, total shoot mass, and new root mass as compaction increased at the dry water content. At dry water content and high compaction, foliar nutrient concentrations were greatest. Generally, water content had a greater impact on seedling growth than did compaction, at the levels of compaction used in this study. This study indicates that if there is a critical value for mechanical impedance of the conifer roots, it likely occurs below 2500 kPa. Our results are consistent with the explanation that soil strength incrementally affects root growth below 2500 kPa for this soil type. Expensive rehabilitation techniques may not be needed on lightly disturbed soils similar to that used in this study if soil water content is high enough throughout the conifer growing season to alleviate the effects of compaction on soil strength.

Coarse woody debris in the old-growth forests of British Columbia

This paper synthesizes data extracted from the literature and data collected in various studies by the author on the quantity, characteristics, and functional importance of coarse woody debris (CWD) in the old-growth forests of British Columbia (B.C.). There is little agreement in the literature about the minimum diameter of CWD or the number of decay classes recognized. In western North America, five decay classes are commonly used, but recent studies suggest fewer decay classes are preferable. Comparisons among decay classes and biogeoclimatic zones and subzones in B.C. reveal that quantities and volumes are greatest (up to approximately 60 kg/m2 and approximately 1800 m3/ha, respectively), and CWD persists the longest (sometimes in excess of 1000 years) in the Coastal Western Hemlock (CWH) biogeoclimatic zone. The quantity and ground cover of CWD increase with forest productivity. Persistence of CWD has varied from less than 100 to over 800 years in two coastal (CWH and Mountain Hemlock (MH)) and three interior (Interior Douglas-fir (IDF), Interior Cedar–Hemlock (ICH), and Engelmann Spruce – Subalpine Fir (ESSF)) biogeoclimatic zones. Trends in CWD quantity with forest age in managed coastal B.C. forests suggest a U-shaped curve, with greater quantities occurring in recent cutovers than in old-growth forests, and lowest quantities occurring in middle-aged forests. This may be the normal trend in CWD with forest age, with departures from this trend resulting from disturbance- or environment-specific factors. Relatively large amounts of data exist on the characteristics of CWD in the CWH, IDF, ICH, ESSF, and Boreal White and Black Spruce (BWBS) biogeoclimatic zones, but such data for the Coastal Douglas-fir, Sub-Boreal Pine–Spruce, Sub-Boreal Spruce (SBS), and Spruce–Willow–Birch biogeoclimatic zones appear relatively sparse. There have been few studies of the functional role of CWD in B.C. forests, but those studies that have been completed indicate that CWD is an important habitat component for some plant and animal species. A total of 169 plant species, including >95% of all lichens and liverworts, were found to grow on CWD in old-growth forests in the CWH, MH, IDF, ICH, and ESSF biogeoclimatic zones. One third of these species were restricted to CWD. Studies in several biogeoclimatic zones have found that CWD provided preferred habitat for and was associated with higher populations of some small animal species, such as shrews, some voles, and some salamanders, in old-growth forests, but the effects varied with species and biogeoclimatic zone. The nutrient cycling role of CWD is not yet well known, but it currently appears to be relatively insignificant in B.C. old-growth forests. Although it has been considered that CWD could increase mineral soil acidification and eluviation, no evidence for this was found in a study of the CWH, MH, IDF, ICH, ESSF, BWBS, and SBS biogeoclimatic zones. Future studies of the functional role of CWD should consider both scale (square metre vs. hectare) and temporal (changes in CWD with forest age) issues, as studies including these are sparse and both may be important. Key words: biogeoclimatic zones, British Columbia, coarse woody debris, old-growth forests.

N 2-fixation by Sitka alder in a young lodgepole pine stand in central interior British Columbia, Canada

Annual N 2 -fixation by Sitka alder ( Alnus viridis (Chaix) DC. ssp. sinuata (Regel) A.&D. Love) was estimated at 10–15 kg N ha −1 over three growing seasons in a young lodgepole pine ( Pinus contorta Dougl. ex Loud.) stand in the Sub-Boreal Spruce biogeoclimatic zone of British Columbia (BC), Canada. Unlike the ambiguous evidence provided by 15 N natural abundance, the isotope dilution method indicated that >90% of the N in new alder tissues was derived from the atmosphere. Despite low light levels (18.1% of open sky values), alders growing under a mature lodgepole pine canopy (>150-year-old) obtained a similarly high proportion of their N requirements by N 2 -fixation.

Monotropa uniflora: morphological and molecular assessment of mycorrhizae retrieved from sites in the sub-boreal spruce biogeoclimatic zone in central British Columbia.

Plant species in the subfamily Monotropoideae are achlorophyllous and have developed a complex mode of nutrition, receiving photosynthates from neighboring trees via shared fungi. To explore the mycorrhizal associations of Monotropa uniflora in central British Columbia (B.C.), plants were sampled from three sites: a Betula-dominated site and two sites with a mixture of conifer and hardwood trees. Fifteen M. uniflora root-clusters were sampled (five per site) and the mycorrhizal diversity was assessed using morphological and molecular (PCR-RFLP analysis and DNA sequencing) methods. Both methods showed that root-clusters (often comprising several hundred mycorrhizal tips) belonging to the same plant appeared to involve fungus monocultures in the family Russulaceae. All mycorrhizae exhibited typical Russula morphology and had mantle cystidia. Two root-clusters, one each from sites 1 and 3, lacked one of the two types of cystidia present on all other root-clusters. PCR-RFLP analysis resulted in three fragment patterns for the 15 root clusters. One molecular fragment pattern included the two root-clusters displaying the single cystidium type plus an additional root-cluster with both cystidia types. DNA sequencing of a portion of the ITS2 region of the ribosomal DNA suggests that the three variants represent different species; two of the variants clustered with the hypogeous fungi Martellia and Gymnomyces. The study provides increased evidence of low diversity and high specificity in the Monotropa-fungus relationship and suggests that M. uniflora associates uniquely with fungi in the family Russulaceae in central B.C.

Site index conversion equations for mixed trembling aspen and white spruce stands in northern British Columbia

White spruce and trembling aspen are two important commercial species in British Columbia. They often grow in association, particularly in the Boreal White and Black Spruce and Sub-Boreal Spruce biogeoclimatic zones. Site index conversion equations are useful for estimating the site index of one species from the site index of another species. This study fills a need for site index conversion equations for mixed spruce/aspen stands. Seventy 0.01 ha study plots were established in mixed spruce/aspen stands. One site tree of each species was selected from each plot. The height and breast height ages of the site trees were measured and the site index was estimated with these data. The correlation between the site index of spruce and aspen was 0.6. Geometric mean regression was used to estimate the parameters of a linear site index conversion equation. The analysis did not reveal any differences in the conversion equations across the three major biogeoclimatic units (BWBSmw1, BWBSmw2, and SBS) that were sampled. Therefore, only one conversion equation is required.

Site Preparation for Establishing Interior Spruce in British Columbia: Trials at Upper Coalmine and Mackenzie

Abstract Two trials (“Upper Coalmine” and “Mackenzie”) were begun in the 1980s in the Prince George Forest Region, B.C., to evaluate a total of 13 site preparation treatments for establishing interior spruce (Picea glauca × engelmannii) in the Engelmann Spruce-Subalpine Fir and Sub-Boreal Spruce biogeoclimatic zones. Treatments included mounding (with various thicknesses of mineral soil “capping”), patch scarification, blading, disk trenching, and herbiciding. In each trial, five blocks each contained one 48 or 80 tree plot/treatment. Trees were monitored for 10 yr at Mackenzie and 15 yr at Upper Coalmine. Large mounds have had consistent biological success. Tree seedling response to blading was site specific; blading at Mackenzie was not significantly inferior to the best (Ministry mound) treatment, but at Upper Coalmine was no better than the untreated control. West. J. Appl. For. 16(1):9–17.

Response of soil CO2 and O2 concentrations to forest soil compaction at the Long-term Soil Productivity sites in central British Columbia

The concentrations of soil CO2 and O2 at three Long-term Soil Productivity sites located in the Sub-Boreal Spruce biogeoclimatic zone of British Columbia, Canada, were monitored over several growing seasons. These sites were treated with three levels of soil compaction and three levels of organic material removal following forest harvest. Both compaction and depth had a significant effect upon soil CO2 concentrations and average values increased in response to deeper sampling and compaction. Removal of the forest floor and other organic materials had no significant effect upon soil CO2 and O2 concentrations. Mean soil CO2 concentrations varied from site to site and data collected over three growing seasons also showed that mean CO2 values in response to compaction fluctuated significantly from year to year. The high levels of soil CO2 observed in this study (up to 40 000 µ L L−1), especially in response to the compaction treatments, may have had a substantial effect upon whole plant carbon allocation as well as soil nutrition available to trees growing on the treated plots. Although mean soil O2 also decreased in response to compaction and sampling depth, these lower concentrations did not approach the levels required to influence plant growth. Key words: Soil, compaction, carbon dioxide, oxygen, long-term soil productivity

Use of understory vegetation in classifying soil moisture and nutrient regimes

One-hundred-and-two white spruce [Picea glauca (Moench) Voss] stands sampled in the sub-boreal spruce biogeoclimatic zone of British Columbia were used to examine the role of understory vegetation in assessing soil moisture and nutrient regimes. Based on the existing knowledge, each species of indicator value was assigned into one of six indicator species groups for soil moisture and/or one of three indicator species groups for soil nitrogen. On each stand, the frequency of each indicator species group was calculated using % covers of all indicator species. Soil moisture and nutrient regimes were then classified based on calculated frequencies following the criteria proposed in the study. As a result, 16 stands were classified as moderately dry, 27 stands slightly dry, 25 stands fresh, 15 stands moist, 12 stands very moist, and 7 stands as wet; 10 stands were classified as very poor, 20 stands poor, 41 stands medium, 24 stands rich, and 7 stands as very rich. These classifications compared favorably with the two soil-based classifications reported earlier for the same data, with 47-59% of stands in agreement and 38-46% of stands in disagreement in only one class. Testing the classification against soil moisture and nutrient measures and white spruce foliage nitrogen and site index further supported the indicator plant approach to soil moisture and nutrient regime classification. It is concluded that the indicator plant approach is a good alternative to the soil-based approaches that have been commonly applied in site classification systems across Canada.

Insect Succession on Buried Carrion in Two Biogeoclimatic Zones of British Columbia

We established a database of insect succession on buried carrion in two biogeoclimatic zones of British Columbia over a 16-month period beginning June 1995. Pig (Sus scrofa L.) carcasses were buried shortly after death in the Coastal Western Hemlock and Sub-boreal Spruce biogeoclimatic zones of British Columbia. Buried pigs exhibited a distinct pattern of succession from that which occurred on above-ground carrion. The species composition and time of colonization for particular species differed between the two zones. Therefore ideally, a database of insect succession on buried carrion should be established for each major biogeoclimatic zone. We did not observe maggot masses on any of the buried carcasses; therefore, the presence of maggot masses may indicate a delayed burial. Soil temperature was a better indicator of internal buried carcass temperature (r2 = 0.92, p < 0.0001) than was ambient air temperature (r2 = 0.60, p < 0.0001); thus soil temperature should be used to determine developmental rates of insects for determination of the postmortem interval by a forensic entomologist.

Resistance of white spruce to white pine weevil: Development of a resistance index

An index of resistance in white spruce, Picea glauca (Moench) Voss, to attack by the white pine weevil ( Pissodes strobi Peck) was developed based on tree variables which measured attack intensity, severity and the tolerance of the tree to attack. The index, derived using principal component analysis, was used to screen 139 white spruce families from the interior of British Columbia in a replicated family trial, for resistance to weevil attack. The resistant ranking of the families was significantly related to the habitat characteristics of the parent trees as measured by elevation, longitude, latitude and by the ecological variables of biogeoclimatic zone, subzone and variant. Geographic sources of white spruce genotypes resistant to weevil attack were identified. These were mainly in the moist-warm habitats of the SubBoreal Spruce biogeoclimatic zone.

Estimating Dominant Height and Site Index of Even-Aged Interior Douglas-Fir in British Columbia

Abstract Height-age and site-index curves were developed from stem analysis of 262 Douglas-fir trees (Pseudotsuga menziesii var. glauca) from 68 plots in the Interior Douglas-fir, Interior Cedar-Hemlock, and Sub-boreal Spruce Biogeoclimatic zones in the interior of British Columbia. Plots ranged in site index from about 8 to 30 m and in age from about 60 to 350 years; however, the analyses were limited to data up to 100 years of age. A conditioned logistic function was selected for predicting height, and a linear model was selected for predicting site index. The curves are similar to those developed in comparable studies in the Inland Empire, but differ substantially from curves developed in British Columbia from temporary sample plots. This study supports previous observations that the pattern of height growth for a given site index varies among ecologically different areas. West. J. Appl. For. 7(1):20-25.